Explosive shell with base detonating fuse



` Nav. 25,` 1969 ExPLosvE SHELL WITH BASE DETONATING FUSE L. BIRKIGT Filed June 7. 1968 United States Patent O Int. Cl. F42b 1]/22, 13/12; F42c 15/00 U.S. Cl. 102-56 3 Claims ABSTRACT OF THE DISCLOSURE The constituent elements of the mechanism of the base detonating fuse, instead of being housed in a separate casing which is then inserted in a housing formed in the base of the shell, are mounted directly in such a housing previously arranged to be able to receive the constituent elements in question.

The present invention relates to explosive shells with a base deto-nating fuse, that is to say to explosive shells comprising, towards the rear, a fuse adapted to assure the firing of the charge of the shell in case of impact; in addition, this fuse can advantageously be arranged in a manner to cause the destruction of the shell after a certain Hight time and to confer on the shell a trajectory safety, sometimes called muzzle safety, guarantying a certai-n ight distance, without the possibility of firing, from the muzzle of the gun. The invention is more particularly, -but not exclusively, concerned with shells of this type which are spin-stabilized, of small calibre (in particular of a calibre comprised between 20 and 50 millimeters), and equipped with a ibase detonating fuse provided with delay means adapted to confer on the projectile a trajectory safety due to the progressive unwindi-ng of a spiral strip under the action of the centrifugal forces brought into play by the spin of the projectile about its axis.

The chief object of the present invention is to provide shells of this type which fulll the requirements of practice Vand which have, radially, an increased volume for housing the constituent elements of the mechanism of their base detonating fuse.

According to the principal feature of this invention, in the shells of the kind in question, instead of housing the constituent elements of the mechanism of the base detonating fuse in a casing which is then inserted into a housing formed in the base of the shell, these constituent elements are mounted directly in such a housing which was previously arranged to be `able to receive the constituent elements in question, whereby the piece formed by the casing of the conventional base detonating fuses is economized, and a gain of volume, radially, corresponding to the wall thickness of that casing is realized for the fuse mechanism.

Other features Vand advantages of the invention will become apparent from the following complementary description, given merely Iby way of example, with reference to the accompanying drawing, in which the single figure represents, in axial section, a spin-stabilized explosive shell with a base detonating fuse, constructed according to one embodiment of the invention.

The invention is particularly applicable to a spinj stabilized explosive shell of small calibre (calibre comprised between 20 and 50 millimeters, for example 30 millimeters) comprising a base detonating fuse capable of conferring on this shell a trajectory safety, and preferably as well, of Iassuring the self-destruction of the projectile after a certain flight time.

ICC

Until the present time, the base detonating fuse ofl such shells was constructed in the form of an independent ensemble comprising a casing at the interior of which Were lodged the constituent elements of the mechanism of the fuse, this casing being then inserted and fixed in the manner of a base plug in `an axial housing, open towards the rear, formed for this purpose in the base of the shell.

This manner of proceeding presented, among other disadvantages, the disadvantage of using a supplementary piece, namely the casing of the fuse, encumbering the peripheral zone of the housing formed in the base of the shell to the detriment of the space available for the constituent elements of the mechanism proper of the fuse and for the evolution of certain of these elements. Moreover, the central zone of the rear end of the base of the shell was unavailable, which rendered the possible adaptation of a tracer device more complicated.

The principal feature of the invention has precisely for its object to mitigate the disadvantages mentioned above.

According to this principal feature, as illustrated in the drawing, instead of housing the constituent elements of the mechanism of the base detonating fuse in a casing which is then inserted in the base 1 of the shell, these constituent elements are mounted directly in a housing 2 formed in the base and arranged to receive the constituent elements in question.

In this manner, on the one hand, the supplementary piece that the casing (of the prior art fuses) constituted is economized (gain of cost price and of weight), and on the other hand, and above all, a gain of volume is realized, in the radial direction, for housing the constituent elements of the fuse mechanism proper and for the expansion of certain of these elements, in particular the expansion of a spiral strip, as will be more explicitely indicated hereafter with respect to a type of base detonati-ng fuse to which the invention is applicable in a particularly advantageous manner.

Moreover, if, according to a more particularly advantageous embodiment, the housing 2 is open towards the front only, that is to say if the base 1 has a solid bottom 1a whose rear end is entirely free, this rear end can receive an axial tracer 3 fixed for example by screwing or crimping.

To illustrate the foregoing, there will now be described, with reference to the drawing, an application in which the invention is applied to a certain type of shell, and an embodiment of the fuse mechanism which is particularly advantageous for putting the invention into practice.

This application concerns Van explosive shell whose base 1, for example of steel (with its solid bottom 1m and its housing 2 open towards the front), plays the role both orf a body for the shell and of a casing for the constituent elements of the base detonating fuse. This base 1 can comprise a driving band formed in a single piece (integral) with the base, or can serve as a support for at least one separate driving band 4, for example of sintered iron. The base 1 serves as a support in addition for a rst charge 5 of explosive, preferably precompressed, and for a cap in the form of an ogive 6 (made for ex-` ainple of drawn steel or of any other appropriate material, for example a plastic material) force fitted on the front skirt 1b of the base 1 and housing a second explosive charge 7 preferably protected on the side towards the nose of the shell by a plastic piece 8. This second explosive charge 7 can contain hard fragments such as darts (for example from 50 to 100 darts of the order of 25 millimeters in length and two millimeters in diameter for the 30 millimeter calibre envisaged).

As for the embodiment of the fuse mechanism incorpo rating self-destruction and trajectory safety, it concerns a mechanism in which an axial tiring pin 9, urged by a spring towards a detonator 11 disposed in front of this firing pin in a first explosive charge 5, is subjected to the action, on the one hand, of a self-destruction device comprising retaining balls 12 mounted free in radial channels 12a formed in the body of the firing pin 1, these lballs 12 bearing, under the effect of the centrifugal forces brought into play by the spin of the projectile about its axis, against a trunconioal ramp 13 having its large base directed towards the rear, these balls counterbalancing the action of the percussion spring 10 as long as the speed of spin of the projectile remains greater than a predetermined value, whereas, below this value, the spring 10 becomes predominant and causes the percussion of the detonator 11 and, consequently, the self-destruction of the projectile, and on the other hand, of a delayed release locking device comprising essentially a spiral strip 14, wound coaxially in front of a shoulder of the ring pin 9 and playing, by its rear edge, the role of an axial stop for the firing pin 9, this spiral spring being retained towards the front by a transverse partition 15 and maintained at its periphery by an expansible split ring 16 adapted to release the strip in question, after the shot is tired, under the action of the centrifugal forces.

It should be noted that the unwinding of the spiral strip 14 under the effect of the centrifugal forces can advantageously be `braked by an inertia sleeve 17, mounted rotatably on the body of the firing pin 9 between this body and the spiral strip, and angularly coupled to the inner end of this strip.

With such a spiral strip type locking system, when the shot is fired and once the split ring 16 has been released by expansion, the spiral strip 14 unwinds progressively driving the sleeve 17 which it abandons during the unwinding of its last turn, the whole spiral strip thus unwound then lying against the peripheral wall of an annular chamber 18 reserved in the rear part of the transverse partition 15. In this unwound position, the spiral strip 14 ceases to play the role of an axial stop for the firing pin 9 which is then free to advance to assure the percussion, either in ease of impact against an objective, or when the action of the self-destruction device with its retaining balls 12 ceases to be predominant.

Such a fuse mechanism comprises essentially coaxial pieces of revolution and its adaptation in the housing 2 formed in the base 1 necessitates only a very simple arrangement of the lateral wall of this housing which can assume a generally cylindrical form with, at a certain height, a thread permitting the fastening of the transverse partition 15.

This transverse partition 15 can then be constructed in the form of a threaded plug extended towards the rear by a skirt 15a bearing against a ring 19 itself bearing against a shoulder of the housing 2, the inner rear edge of this ring 19 being chamferred in a manner to form the trunconical ramp 13.

Once the fuse mechanism has been mounted in the base 1, this fuse mechanism can be protected at the level of the driving band 4 by a ring 20 adapted to oppose the lateral wall of the base from collapsing (in particular if this wall is relatively thin) when the driving band 4 is forced into the rifling grooves of the barrel of the gun. The mounting of the shell is completed by putting in place the charge 5 and the cap 6 previously fitted with the charge 7.

It will be appreciated that for such a base detonating fuse, exempt of an autonomous casing (the fuse body taking the place of the casing), it is possible, other things (in particular the calibre and the thickness of the wall of the fuse body) lbeing equal to achieve a substantial gain of space, in the radial direction, for the annular chamber 18 in which the unwinding and the expansion of the spiral strip 14 takes place.

This gain permits, with a spiral strip of given thickness, a greater number of turns to be given to the spiral strip, and consequently, the trajectory safety conferred by the fuse to be increased.

By way of example, and solely to bring out more clearly the advantages of the invention, it can be mentioned that, by using a lmetallic spiral strip (for example made of brass foil) of a thickness of 0.08 millimeter, the strip was limited, in the case of a conventional base detonating fuse with a separate casing in the base of the shell, t0 l0 turns providing a trajectory safety of 5 meters, whereas, in the case of a shell with a base detonating fuse incorporated without a casing, according to the invention, it is possible to give, to the same type of strip, 30 turns providing a trajectory safety of the order of 20 meters.

Whatever embodiment is adopted, a spin-stabilized explosive shell with a base detonating fuse is provided whose operation and advantages result suiciently clearly from the description which has just been given, that no further explanation is necessary in this connection.

The invention should not be limited to the particular application nor to the particular embodiment described by way of example. Various modifications are possiblesuch as a modification in which the fuse mechanism is of a type other than that described by way of example, for example a Spiral strip type firing pin mechanism having a primer housed in a rotor movable from a position in which it blocks the firing pin to a position in which it permits the tiring pin to strike the primer-without departing from the spirit or scope of the invention.

What I claim is:

1. An explosive shell comprising a base, an explosive charge carried at the front of said base, and a base detonating fuse carried at the interior of said base, said base detonating fuse comprising a fuse mechanism comprising a plurality of constituent elements, wherein said base comprises a front skirt and a ybottom at the rear of and unitary and integral with said front skirt, said base thus forming a housing, said housing receiving the constituent elements of the base detonating fuse, said constituent elements being mounted directly in said housing without the intermediary of a separate casing, said housing being open towards the front of said base and at least partially closed at the rear by said unitary, integral bottom, which bottom axially supports said fuse from the rear, whereby the constituent elements of said fuse mechanism can be put in place only from the front.

2. An explosive shell according to claim 1 wherein said housing -is completely closed at the rear by said unitary, integral bottom.

3. A spin-stabilized explosive shell according to claim 1, wherein said fuse mechanism comprises a delayed release locking device comprising essentially a spiral strip adapted to unwind under the effect of centrifugal force to occupy an inactive position.

U.S. Cl. X.R. 

